An increasing number of lighting applications have been developed utilizing LEDs because of their ruggedness (they are solid state devices), their compactness, their low power requirements and their long life. Foremost among these light applications have been the light sources used in automotive vehicles; namely, center high mount stop lights (CHMSL) and tail and brake lights. In some applications the LEDs are suitable for use as direct-view light sources, comparable to the S8 filamented lamps they replace. However, in other applications it is desirable to collect the light from the light source and concentrate and/or focus it so that it can be directed to a remote location, for example, via a light guide. Light guides do not focus or concentrate the light received by them, but merely direct it to another location. It has long been known that an optic with a parabolic surface generated by the standard formula, Z=¼f·R2, such as those used in PAR lamps, is an efficient concentrator of light and such devices have been used in the past with light emitting diodes; however, generally, each light emitting diode was utilized with an individual optic, a costly and difficult procedure compounded by alignment issues. It has been proposed to utilize a single optic with an array of LEDs for purposes of automotive headlamps, wherein a high luminance, a narrow radiation angle and a well-defined shape of radiation is used. See US Published Patent Application No 2009/0001490 A1 (Bogner, et al.). Also, direct importation of light from LEDs into a light guide or guides is known in US Published Patent Application No. 2009/0185389 A1 (Tessnow, et al.), which application is assigned to the assignee of the instant invention.
Adaptation of parabolic optics for leading light into light guides has, however, proven difficult, particularly when involving a linear array of LEDs. For example, it has been know to use a single glass compound parabolic concentrator (CPC) for each LED in a 2×3 chip array; however, such a system does not work well with a tightly spaced linear array.
Additionally, utilizing a linear array of LEDs has also proven difficult. Beginning with a linear array, one is generally limited to a particular entrance, the size of the entrance, of course, being dictated by the physical dimensions of the array itself. Developing a specific exit aperture for such an array, using a conventionally oriented CPC, has been found not practicable.